KR100831456B1 - Data flow control in wlan radio connections for the impairment of internet telephony - Google Patents

Abstract

The present invention relates to a method of controlling data flow in a wireless connection between a WLAN base station and a WLAN mobile station, wherein the data rate of the wireless connection is reduced during one time period (36,37) in the interval (35). A preferred application for this method is to limit the general or unauthorized sending of telephone calls over the Internet.

Description

DATA FLOW CONTROL IN WLAN RADIO CONNECTIONS FOR THE IMPAIRMENT OF INTERNET TELEPHONY}

The invention relates to a method and apparatus for controlling data flow on a WLAN wireless link, as claimed in the independent claims.

Mobile speech communication is handled primarily through cell-based mobile radio networks. In Europe, such cell-based mobile radio networks are based on the GSM standard or the UMTS standard. These mobile wireless networks are costly to use because users are charged based on talk time.

In contrast, the main field of application for wireless local area networks, also referred to as WLANs, is non-speech-oriented data transmission. In this case, WLAN is a generic term that represents many different standards for local wireless networks. In particular, they have developed a variety of standards from the IEEE-802.11 working group (e.g., IEEE-802.11b or IEEE-502.11e), the Bluetooth Standard, the HomeRF Standard, and the HyperLAN Standard. Include.

As such WLANs, especially WLANs for the IEEE-802.11b standard, are increasingly used, so-called hot spots are located in public places. So-called hotspots occur within a radio range around an IEEE-802.11 compatible WLAN base station, also referred to as a WLAN access point, in which case the wireless link uses, for example, a WLAN wireless network card. It can be set up in a hotspot between a WLAN compatible mobile device and a WLAN compatible mobile device such as a laptop. WLAN access points also connect to wired networks, for example, via a wire-based Ethernet interface. The Internet can be accessed through this wired based interface. Therefore, when within the propagation distance of a WLAN access point, a user of a WLAN compatible mobile device can access the Internet through the WLAN access point. In some cases, the fee for using this infrastructure is free, based on the amount of data, access time, or at a flat rate.

Internet telephony, also referred to as Voice over Internet Protocol (VoIP), can be operated by accessing the Internet via a WLAN access point. In this case, voice information is transmitted and received on a packet basis through the Internet. VoIP specifies a plurality of requirements for both the transport channel, i.e., the wireless link between the WLAN base station and the WLAN access point, and the wire-based link between the WLAN access point and the communication partner. Compliance with these requirements and requirements is also referred to as Quality of Service (QoS). One particular requirement in this case is whether it is possible to ensure a data rate suitable for the transmission of voice information. Another requirement is whether the delay of the transmission channel remains constant in time so that the transmission signal does not have short jitter. As another essential requirement for the transport channel, it is necessary to ensure that the delay time of the channel remains below a threshold that is still acceptable for voice communication. In this case, in particular, the bidirectional delay time between the transmission of the information item over the transmission channel and the reception of the information item based on the transmitted information, also commonly referred to as a "round trip delay" (RTD), is usually less than 100 ms. It is necessary to take into account the fact that it must exist within the scope of.

If the transport channel does not meet the above requirements, the VoIP application will be subject to major quality constraints. If the requirements of the transport channel are met, voice communication over the cell-based mobile wireless network can be replaced by VoIP. In this case, voice communication in the wireless area of the WLAN access point may be performed at a fairly low cost over the WLAN instead of cell-based mobile wireless networks, or even free of charge. This creates a competition between WLAN wireless networks based on IEEE-802.11 and cell-based mobile wireless networks. Operators of cell-based mobile wireless networks also run WLAN hotspots, so this competition also occurs inside operators. Because VoIP calls over a WLAN wireless link based on IEEE-802.11 are cost-effective compared to calls over GSM or UMTS mobile radios, the risk of cell-based mobile radio replacement is reduced.

The IEEE-802.11e standard, which is not yet finalized, will provide new access methods that allow improved QoS, particularly for VoIP applications, by properly prioritizing data traffic. In such a case, in order to limit VoIP traffic, it would be possible to make the enhanced QoS available only to suitably authorized users. However, since enhanced QoS is not absolutely necessary for VoIP applications when the load level on the WLAN access point is low or medium level, VoIP traffic is limited by the selective provision of enhanced QoS or It cannot be monitored.

In principle, a WLAN access point cannot distinguish whether data traffic over a wireless link between a WLAN mobile station and a WLAN access point is dominated by VoIP based data or non-voice based data. Therefore, it is impossible for a WLAN access point to block the WLAN radio link for unauthorized VoIP based data.
International Patent Application Publication No. 03/04327 A discloses a method of providing a quality of service for which the limitation on data rate is user-specified.
G. Series: "Transmission Systems and Media, Digital Systems and Networks" discloses the maximum limit on the allowable delay for the transmission of voice signals.

It is therefore an object of the present invention to specify a technical method that enables synchronous data traffic to be compromised or limited, in particular between WLAN base station and WLAN mobile station by VoIP based data. In this case, this method is not intended to interrupt asynchronous data traffic from the perspective of the WLAN mobile station user by existing Internet applications such as surfing and e-mail on the WWW, for example.

The object on which the invention is based is achieved by the features of claim 1.

In a method for controlling data flow on a wireless link between a WLAN base station and a WLAN mobile station, in accordance with the present invention, the data rate on the wireless link is in each case reduced for one time period in time periods.

This method is used to limit synchronous data traffic on the wireless link. Synchronous data traffic may be based on various synchronous applications or services, such as pure voice based VoIP or video conferencing, for example.

The preferred area of application for this method is to prevent universal or unauthorized sending of telephone calls over the Internet. In this case the method according to the invention is based on the fact that synchronous data traffic can only be ensured if the data rate of the WLAN radio link is kept at a value corresponding to the amount of data occurring in synchronous form per unit time. If this is not guaranteed, even for a short time, synchronous transmission of data is adversely affected. According to the present invention, if the data is reduced only for a short time period in a randomly selected or fixed selection time period, this will constantly adversely affect the synchronous data transmission. When using the method according to the present invention, the quality of the VoIP link is drastically degraded, so that the user has to return to the infrastructure of a cell-based mobile wireless network for a telephone call. However, when using the method according to the invention, the average data rate of the WLAN radio link is only slightly reduced or not at all compared to data transmission without the method according to the invention. Asynchronous data traffic using the same existing Internet application is not adversely affected by WLAN mobile station users. For the purpose of the application, the data rate can be reduced in one direction and in both directions. In principle, in a two-way VoIP link, it is possible to reduce only the data rate of data received from the WLAN mobile station or data transmitted to the WALN mobile station, since in both cases the RTD increases.

For this application, the expression WLAN base station or WLAN mobile station should be understood to mean a network node in any desired WLAN, in particular a network node that is compatible with the IEEE-802.11 working group standard (eg, IEEE-802.11b). For simplicity, this standard class is referred to in the following with the expression IEEE-802.11 standard.

In this case, this method is advantageously performed at the WLAN base station. Therefore, all that is needed to implement the method according to the present invention resides in the WLAN base station, so that in order to carry out the present invention, no requirement due to the present invention needs to be located in the WLAN mobile station. Therefore, this method can be used for wireless traffic using existing WLAN mobile stations without any changes to the WLAN mobile stations.

If the time duration and / or time period changes over time, the duration of the data rate reduction at a given time should be shorter than that time period.

The repeated reduction in data rate is advantageously implemented in such a way that the data on the wireless link is delayed by the delay time. In this case, since no data is transmitted during the delay period, the time delay corresponding to the delay time period actually operates as the data rate decreases to zero at a predetermined time. Since all that is needed in this case is to disturb the data traffic during the period of latency, the dynamic reduction of the data rate can be implemented with the help of a particularly small repetitive delay. In particular, it is possible to have the delay time chosen arbitrarily so that in other cases a user who can respond can not identify any system in adverse effects.

Iterative delay is advantageously applied without intervening in the radio-specific OSI layer. To this end, the repetitive delay of the data is implemented in such a way that further processing of the data received from the wired network side and assigned to the radio link to the WLAN mobile station is delayed over time. In this case, further processing relates to the data being temporarily stored in buffer storage located within the WLAN base station and allocated to the radio link. Preferably the buffer storage is FIFO (first-in, first-out) memory. This may be provided as a FIFO queue in software or hardware, for example in the form of a FIFO ring memory.

In this way, delay data provides the advantage that delay can be implemented without intervening in a radio-specific layer such as a medium access control (MAC) layer or a physical layer. Therefore, for example, in the IEEE-802.11 standard, no change is necessary at the radio station to carry out this method. Since each radio link between a WLAN base station and a WLAN mobile station can utilize only one and one dedicated buffer storage or buffer storage area, the procedure of the method according to the invention is based on user-specific, in particular specific users. It can vary depending on the nature of the data delay being deactivated for. If the buffer storage is FIFO memory, the first-in, first out (FIFO) principle means that no data has been lost, so even if there is a delay, it needs to process any additional numbers to ensure the integrity of the data flow. Neither is there any change in the data sequence. As already described above, such buffer storage may be implemented on a software basis or on a hardware basis. For example, the delay may be implemented by activating a switchable delay element downstream from the buffer storage over time.

In order to delay the further processing of this data, it is possible that the data output of the data which was received at the wired network side from the buffer storage, in particular the FIFO memory, is suppressed at a time corresponding to the delay time.

It is fairly straightforward to implement delays by timely suppressing data output from buffer storage without any additional delay factor. In particular, the data output can be suppressed by setting a signal controlling the data output from the buffer storage during suppression so that no new data can be read from the buffer storage. Once the control signal activates the read process again after the delay time, the data read from the buffer storage is the data already waiting to be output at the same time as the data output was suppressed.

The duration of the delay is advantageously in the range of 100 ms to 5 s, in particular in the range of 100 ms to 1 s. This selection of time period or delay time does not interfere with asynchronous data traffic in terms of WLAN mobile user. However, synchronous data traffic is severely affected because of the increase in the RTD associated with this selection of time period or latency, so that VoIP can no longer be implemented in an effective manner. The time period is advantageously in the range of 500 ms to 15 s, in particular in the range of 1 s to 10 s.

According to one advantageous embodiment of the method according to the invention, the user status of the WLAN mobile station is first checked. The data rate on the wireless link then decreases only when the user state does not allow the use of synchronous data services such as, for example, VoIP. If the user state permits the use of the synchronous data service, then the reduction of repeated data rates in accordance with the present invention is deactivated.

Selective activation or deactivation of data rate reduction according to the present invention as a function of user status makes it possible to provide only the WLAN mobile station users with the QoS required for the use of synchronous services, for example, VoIP. In this case, the authorization may be associated with the payment of a particular fee. These users who are not licensed based on the user status are actually prohibited from using the synchronous service due to the reduction of data rate according to the present invention.

The device according to the invention as set forth in claim 12 is designed to control the flow of data on a wireless link between a WLAN base station and a WLAN mobile station. The apparatus has means for reducing the data rate over time.

A WLAN station according to the invention as set forth in claim 14 comprises a device according to the invention. The WLAN station may be a WLAN base station or WLAN mobile station. The device according to the invention is preferably integrated in a WLAN base station.

Other preferred refinements of the invention are specified in the dependent claims.

The invention will be described in greater detail in the text that follows using exemplary embodiments and with reference to the drawings.

1 shows a block diagram of an implementation of a method according to the present invention for a WLAN access point operating based on the IEEE-802.11 standard.

2 shows two time profiles for a radio link with or without a short delay in transmission.

1 shows an implementation of the method according to the invention for a WLAN access point 1 operating based on the IEEE-802.11 standard. WLAN access point 1 represents an access point for WLAN mobile stations 2 and 3 which are within a propagation distance to access the Internet 4. In this case, one WLAN access point 1 forms a wireless network with WLAN mobile stations 2,3. In this case, as an example, one WLAN mobile station 2 or 3 may exist in the form of a laptop, personal digital assistant (PDA) or existing GSM or UMTS mobile telephone having an IEEE-802.11 compatible wireless interface. In this case, the applications 5 and 6 are executed in the WLAN mobile stations 2 and 3 respectively by exchanging data using the Internet 4 required for both the applications 5 and 6. For example, application 5 or 6 may be in the form of surfing in VoIP or WWW. The data interchange for the application 5, 6 in this case is located in each WLAN mobile station 2, 3, respectively, in the transceiver 11 located in the WLAN access point 1, in particular in the WLAN access point 1. Through individual WLAN transceivers 7 and 8, respectively, connected via wireless links 9 or 10. As described in more detail below, data associated with the wireless link 9, 10 is supplied to the Ethernet transceiver 13 (separated based on the receiving or transmitting direction) via the WLAN / Ethernet interface 12, and the Ethernet transceiver The output is from 13 to the WLAN transceiver 11.

By way of example, the Ethernet transceiver 13 may be connected to 10BaseT (10 Mbit / s), 100BaseT- (100 Mbit / s, also referred to as Fast Ethernet) or 100Base-Standard (1 Gbit / s, also referred to as Gigabit Ethernet). It works based on The Ethernet transceiver 13 accesses the Internet 4 via a transmission medium 22 (eg, glass fiber or coaxial line). The WLAN access point 1 allocates the data packet 14 received by the Ethernet transceiver 13 via the demultiplexer 15 to the parallel FIFO memories 16, 17 for temporary storage. The demultiplexer 15 performs this allocation process as a destination address of each data packet 14, namely, an address of the WLAM mobile station 2 or an address function of the WLAN mobile station 3. In this case, each FIFO memory 16, 17 is associated with one of the WLAN mobile stations 2 or 3. In this case, it is assumed that FIFO memory 16 is associated with mobile station 2 and that FIFO memory 17 is associated with mobile station 3. Data placed in FIFO memories 16, 17 is read through selector 18, also referred to as an arbiter, and then transferred from WLAN transceiver 11 to WLAN mobile station 2 or 3. The control signal 19 for the selector 18 is defined as part of the MAC layer by an access process (eg, based on a distributed coordination function (DCF), a point coordination function (PCF)). The data output from the FIFO memories 16 and 17 is controlled by the respective control signals 20 and 21. At the WLAN access point 1, the data packets 23 received via the WLAN transceiver 11 are written to the Ethernet transceiver 13 via the network 24, which will not be described any further about the application. The WLAN / Ethernet interface 12 may be in the form of hardware, software, or a mixed form. The control signals 20, 21 may therefore be software-internal variables.

The following description is based, first of all, on the assumption that the application 5 in the WLAN mobile station 2 does not generate any synchronous data traffic (eg surf in WWW). In contrast, the application 6 in the WLAN mobile station 3 represents an Internet phone, in which case the synchronous data must be bi-directionally and constantly interchanged between the WLAN mobile station 3 and the corresponding party. When the radio link 9 or 10 is established, the WLAN access point 1 checks the user status of the WLAN mobile stations 2, 3. This information can be checked from the service provider database, for example via the Internet. The data rate on the radio link 9 or 10 then decreases for a while only in a time period where the user state does not permit the use of synchronous data services such as, for example, an internet phone. If this is the case, the data on the radio link 9 or 10 is delayed by a delay time of 200 ms, for example at a time interval of 1 s. According to an exemplary embodiment, this delay relates to further processing of data received via the Ethernet transceiver 13 and stored in the FIFO memories 16, 17.

Referring to Figure 1, the delay is implemented in such a way that the data output from the FIFO memory 16 or 17 is suppressed for a while in the time period. The advantage of this procedure is that there is no need to intervene in the MAC or physical layer of the WLAN interface. Specifically, even if the selector 18 is ready to read data from each buffer storage 16,17 according to the access method (part of the MAC layer), each FIFO memory 16 or 17 during the delay time. A delay is generated by setting each control signal 20 or 21 during the delay time so that no data can be read from. Once the delay time has elapsed, each control signal 20 or 21 is set such that data can be read from each FIFO memory 16 or 17 by the selector 18. Therefore, the data that the selector 18 should actually read at the start of the delay is read after the delay time. This means that data is also received at each mobile station 2 or 3 later. When the method according to the present invention is used compared to the data transmission when the method according to the present invention is not used, the average data rate of the WLAN radio link 9 decreases only slightly or not at all, so that the application 5 It is not adversely affected by short delays occurring over time. The increase in RTD resulting from this result (e.g., 200 ms at a time interval of 1 s) cannot be detected by the user of the WLAN mobile station 2. On the contrary, the quality of the VoIP link in the form of an application 6 is drastically degraded due to the increase in the RTD for the user of the WLAN mobile station 3. The user of the WLAN mobile station 3 must return to his GSM or UMTS mobile station for mobile voice communication.

In another operational state for the WLAN access point 1, it is assumed from now on that both the application 5 in the WLAN mobile station 2 and the application 6 in the WLAN mobile station 3 represent an Internet telephone. While the radio link 9 or 10 is being established, the WLAN access point 1 checks the user status of the WLAN mobile stations 2, 3. In this case, only the user (excellent user) of the WLAN mobile station 2 is permitted to use the Internet telephone, and not the user (standard user) of the WLAN mobile station 3. Data packets received at the Ethernet transceiver 13 and assigned to the mobile station 2 are recorded in the FIFO memory 16 via the demultiplexer 15, while data packets assigned to the mobile station 3 are stored in the FIFO memory 17. Is written on. In this case, the above-described output of delayed data and the transfer of the data are implemented only for the FIFO memory 17. For this purpose, as already explained, the control signal 21 must be set such that the selector 18 cannot read any data from the FIFO memory 17 during the delay time. No delay is provided for the data output from the FIFO memory 16. Therefore, the RTD increases only for the mobile station 3, but does not increase for the mobile station 2 otherwise. Thus, while the quality of the VoIP link in the form of an application 6 is drastically reduced due to the increase in the RTD, the VoIP link in the form of an application 5 is not limited in any way.

For the application, the data transferred from the mobile stations 2, 3 may alternatively or additionally be executed such that the data transmitted from the mobile stations 2, 3 is delayed in a similar manner to the received data. In this case, the network 24 should be designed in a manner similar to the technical theory described above.

FIG. 2 shows two power / time profiles for the radio link 9 or 10 based on FIG. 1, where the time profile relates to data received at the WLAN mobile station 2 or 3. Examples of temporal profiles are provided only to aid understanding of the principles of the present invention and are not to be scaled by actual relationships. In this case, the delay time is the length of one time slot (20 kHz for the 802.11b standard with a data rate of 11 Mbit / s) and the longest length of the MAC frame (the 802.11b standard with a data rate of 11 Mbit / s). It can be several units of larger size than (up to 4095 bytes). The above temporal profile describes a radio link 9 or 10 in which no data delay on the radio link 9 or 10 according to the invention is implemented by the delay time in a time period. In each case, individual data bursts 30 to 34 are transmitted without delay. Alternatively, the time profile below shows the radio link 9 or 10 where the individual data bursts 31 ′ to 33 ′ are delayed by each delay time 36 or 37 in the time period 35. In this case, data bursts provided with the same reference symbol in the upper time profile and the lower time profile are coincident with each other. In this case the data burst 31 'of the underlying time profile is delayed by the delay time 36 compared to the data burst 31 of the upper time profile. Similarly, the data burst 33 'of the underlying temporal profile is delayed by the time profile 37 compared to the data burst 33 of the upper temporal profile. During delays 36 and 37, the data rate drops to zero momentarily. Delay times 36 and 37 may coincide with each other. According to the present invention, the data is temporarily delayed in the time period 35 in such a way that only data bursts 31 'and 33' are delayed over time, not all data bursts.

Claims (15)

A method of controlling data flow in a wireless link (9, 10) having synchronous data traffic and asynchronous data traffic between a WLAN base station (1) and a WLAN mobile station (2, 3), a) reducing the data rate of the synchronous data traffic on the wireless link for one time period 36,37 for each case in time periods 35 to limit the synchronous data traffic. How to control data flow. The method of claim 1, The method is performed at the WLAN base station 1 How to control data flow. The method according to claim 1 or 2, The time periods 36,37 of the data rate reduction at a given time are shorter than the time period 35 at that time in each case. How to control data flow. The method according to claim 1 or 2, The method step a), a ') delaying data on the radio link 9, 10 by a delay time 36, 37, in particular a randomly chosen delay time, in time periods 35. How to control data flow. The method of claim 4, wherein The method step a ') a '') buffer storage 16, 17, in particular FIFO memory, received at a wired network end, assigned to the radio link, located at the WLAN base station 1 and allocated to the radio link 9, 10. Delaying further processing of data temporarily stored in the server; How to control data flow. The method of claim 5, wherein The method step a '') is Suppressing data output of the data that has been received at the wired network end from the buffer storage 16, 17, in particular a FIFO memory, at a time corresponding to the delay times 36, 37. How to control data flow. The method according to claim 1 or 2, The time period or delay time 36,37 is in the range of 100 ms to 5 s, in particular in the range of 100 ms to 1 s. How to control data flow. The method of claim 7, wherein The time periods 35 range from 500 ms to 15 s, in particular from 1 s to 10 s. How to control data flow. The method according to claim 1 or 2, The time period or the delay time and / or the time period varies over time How to control data flow. The method according to claim 1 or 2, b) checking the user status of said WLAN mobile station (2,3), Determining whether the method step a) has been performed according to the check result from the method step b) How to control data flow. The method according to claim 1 or 2, The synchronous data traffic is voice over IP (VoIP) traffic. How to control data flow. 1. An apparatus for controlling data flow on a wireless link 9, 10 having synchronous data traffic and asynchronous data traffic between a WLAN base station 1 and a WLAN mobile station 2, 3. Means for reducing the data rate of the synchronous data traffic for one time period in a time period to limit the synchronous data traffic; Data flow control unit. The method of claim 12, The means for reducing the data rate (16 to 21; 24) comprise buffer storage, in particular FIFO memory (16, 17) for temporary storage of received or transmitted data, and control associated with the buffer storage. A signal (20, 21) to inhibit the data output from the buffer storage (16, 17) at times Data flow control unit. With the device as claimed in claim 12 or 13 WLAN station. The method of claim 14, The WLAN station is a WLAN base station 1 WLAN station.

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